1. Field of the Invention
The invention relates to integrated circuit devices. More particularly, the invention relates to variable capacitors within integrated circuits.
2. Description of the Related Art
Integrated circuits typically provide many performance advantages when compared with discrete designs. However, process parameter variation during manufacturing often results in frequency responses that differ significantly from design. Furthermore, certain discrete elements have proven to be difficult to integrate effectively into conventional complementary metal-oxide semiconductor (CMOS) technology.
An example of such an element is a varactor or varactor diode, which is an element whose capacitance varies with the voltage applied thereto. The varactor provides tuning control for devices such as LC-based voltage-controlled oscillators (VCOs). Common metrics for varactors include quality factor (Q) and tuning range, and most of these variable capacitance devices are purchased as discrete components.
However, to continue the drive toward integration, it is advantageous to have available variable capacitance elements such as varactor diodes that are capable of providing high-performance and are capable of being readily integrated into a common CMOS technology.